1. Field of the Invention
The present invention concerns the field of automation and computer engineering. It concerns in particular an inductional, semi-automatic method for reading the coordinates of three-dimensional objects (scale models, models) with a complicated structure and the input of these data in a computer.
The invention can also be used without any restrictions whatsoever for reading the coordinates of two-dimensional objects (such as drawings, diagrams, maps, etc. ) and for their input in a computer.
2. Description of Related Art
Electromechanical methods are already known for the semi-automatic reading of the information of three-dimensional objects. Such a method is described in the Japanese patent application No 1-94420 for a "computer-oriented reading device for three-dimensional information"; IZOBRETENIA STRAN MIRA 1990, N6, p. 78. The method is based on the use of the three-dimensional pantographical system, whereby use is made of three three-dimensionally moveable levers which are connected to a stationary support and the actual coordinate reading device.
The levers are connected to one another by means of sensors which measure the angular displacement, whose information, taking into account the (known) length of the lever arms, can be used as basic data for the calculation (identification) of the three-dimensional coordinates of a specific point (peak point) of the coordinate reading device, which was superposed by the operator on a point of the object to be measured.
This method is disadvantageous in that it is inaccurate, due to the presence of several sensors which measure the angular displacements (sensors of the "angle-code" type), and the large dimensions of the lever arms which make it difficult to meet the demands of mechanical rigidity, and finally the limited functional possibilities of such devices, due to the mass inertia of the system and the impossibility to measure the complicated inner faces of objects.
The present invention more closely resembles methods based on the use of induction to permit semi-automatic reading of surface and three-dimensional coordinates, such as the method described in the USSR author's certificate No. 550 548 for: "Device for reading graphic information" (BULLETEN IZOBRETENII N 10). This method involves the generation of a variable magnetic field at two points on a coordinate axis which is part of the three-dimensional coordinate system realized with a certain increase in the digitization of the working space; the creation, by means of two magnetometric sensors which are placed along the axis in the coordinate reading device, of the generalized information signal E.sub..SIGMA. =e.sub.1.sup.2 +.sub.2.sup.2 +e.sub.3.sup.2 whereby e.sub.i is the amplitude of the signals which are induced in three (i=1, 2, 3) bi-orthogonal receiver induction coils in each of the magnetometric sensors; a formation of the sequence of digital values of the output signals of the sensors; the identification of the coordinates of the common center of the three bi-orthogonal coils which make up each sensor, referred hereinafter as the sensor "middle points," as the extreme points for the generalized information signals of all value sequences of the coordinate axis; and the calculation of the peak point of the coordinate reading device, placed on the point of the object whose coordinates are being read, according to the following equation: EQU u=u.sub.2 -a/b (u.sub.1 -u.sub.2),
whereby u={x, y, z} and a and b are constants which define the design of the coordinate reading device (a--is the distance between the peak point and the middle point of the nearest magnetometric sensor, b--is the distance between the middle points of the sensors).
The disadvantage of this known method is again its inaccuracy due to mechanical limitations resulting from placement of the coordinate induction coils at 1-2 mm steps to generate the variable magnetic field at specific points in the coordinate system.